1. Field of the Invention
The invention relates to processes for preparing hybrid polyester-polyether polyols from carboxyl group-containing compounds and epoxides. More particularly, it relates to processes for preparing hybrid polyester-polyether polyols optionally using one or more of a double metal cyanide catalyst, a superacid catalyst, a metal salt of a superacid catalyst, and/or a tertiary amine catalyst.
2. Background of the Art
Polyurethanes are produced in large quantities around the world. They are usually produced by reacting polyisocyanates with compounds containing at least two hydrogen atoms which are reactive toward isocyanate groups, in particular, polyether polyols and/or polyester polyols. For various applications, it is advantageous to build both ether groups and ester groups into a single polyol, in order to more conveniently and, in some instances, more economically take advantage of properties imparted by each to a final polyurethane prepared therefrom. Polyols containing both types of groups may be referred to in the industry as polyester-polyether polyols.
Although a wide variety of methods of preparing polyester-polyether polyols have been developed, many suffer from drawbacks. These drawbacks may include the presence of undesirable residual glycol in the polyol, broad polydispersity, poor yields, and required preparation temperatures greater than 150° C. There remains in the art a need for a process to prepare the hybrid polyols that reduces or eliminates these drawbacks.